Wireless networks such as Enhanced UMTS, 802.16e and the like are being designed to support the packet switched (PS) domain only. Traditionally the user equipment, also known as a mobile station or mobile, is either in an active state with a dedicated connection or in a paging or dormant state (i.e. sleep mode) to conserve energy. In paging state, the mobile supports discontinuous reception wherein the mobile sleeps and wakes up at pre-determined intervals to check if the network has paged it. In 3GPP (UMTS) the mobile has an additional CELL_FACH state where it continuously monitors the downlink common control channel for activity.
The paging state, i.e. the discontinuous reception state, helps to conserve battery charge by reducing the average current drain, however at the cost of some latency for downlink transmissions. The mobile can at any time send an uplink signaling message to indicate a need to transmit in the uplink. In CELL_FACH state the mobile is unable to conserve battery charge due to the continuous monitoring of the control channels.
One of the undesirable effects of the discontinuous reception state is that mobile may be better served by a neighboring cell site due to change in radio conditions however the current serving cell site has pending data to exchange with the mobile. If it is determined that the mobile has poor link performance with the current serving cell, typically the current serving cell executes the handover procedure and as part of the handover procedure forwards the data to be exchanged to the target neighboring cell, that is the candidate for handover instead of to the mobile. Then the neighboring cell, once the connection is established with the mobile, sends the data to the mobile. This creates a delay in getting the data to the mobile in addition to having to use extra resources to transfer the data from the current serving cell to the neighboring cell and then to the mobile.
The various aspects, features and advantages of the present invention will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description of the Invention with the accompanying drawings described below.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.